Population Balance Modeling (PBM) - Ansys Fluent
 

Dear Members,

If you have any specific questions on PBM implementation please post here. I will try to answer them, as I gained some experience in it.

on
- Existing module (or)
- Implementation through UDF

hello
 

hello:

i have some problem to implementation pbm(udf)..the problem is that i do not know how to get the bubble number density Ni Nj

Could you clarify more on your problem.

1) What method you are using to solve the PBE ?

Does it neet to multiply ni and nj (luo aggregation kernel)

Hi,

I have a two-phase flow model consisting of liquid(primary phase)-gas (secondary Phase).....now I want simulate the size distribution of solid particles in liquid phase using Population Balance Module available in FLUENT....will this simulation feasible in FLUNET or there is any limitation?...Can you please let me know any work is done in this area (multiphase flow with population balance having three phases)....if exist can you please send me the reference?

PBM model setup
 

Hello,

I need to setup a PBM model for Flame Spray Pyrolysis system. I have some difficulties with setting up the model.
I want to model nucleation, growth and agglomeration.
we use air-assisted nozzle for this. you can see this paper for full details and geometry: ''Nanoparticle synthesis at high production rates by flame spray pyrolysis''.
I used Eulerain multiphase model and QMOM of population balance model.
a liquid mixture of fuel (Ethyanol) and precursor (hexamethyldisiloxane(HMDSO)) are injected from a nozzle in bottom center of the domain and oxidizer (air) also flows up form surrounding of the nozzle.
the reaction products of ethanol combustion all are in gas phase but combustion of HMDSO produces SiO2 solid nanoparticles. we need to models this process by population balance model.
- How many phases we need to define?
- how to link the phases?
- how to set-up nucleation?
it would be grateful if you help me to sort out this.

Thanks,

Hello,

few tips, that may help you.

first approach: Assuming that the particle phase and HMDSO does not influence the flow and chemistry. Then do the spray combustion as usual. in this case, off course you have 2 phases. Freeze this case and data. Now do the particle phase calculations on this fully converged flame. I do not know whether it is possible with the existing QMOM solver, If not, you may need to write a UDF (QMOM solver) for this.

With the existing solver you have always the option to provide your one nucleation, aggregation rates through a UDF. Please check for the corresponding macro in the manual. sth like DEFINE_PB_NUCLEATION_RATE

second approach: is it possible to consider all the reactants also in gas-phase, then you have two phases 1 gas 2 particle.

Third approach: With three phases.

I am sorry I do not have access to Fluent to check and let you know about this.

Thank you for your reply,

what do u mean with freezing the case and data?

I have another question with UDF:
there is such declration in UDF formats in fluent:
solute_mass_frac = C_YI(cell,tp,0);
/* mass fraction of solute in primary phase (solvent) */
do you know what is the YI, does it addressing to any particular specious in primary case, if so, then How can I address for example to N2, if I have mixture of h2o, o2, co2, N2 and ch4 in primary phase?

Thanks,

Hi,
The main purpose of this simulation is to study the Particle Size Distribution (PSD) of BaSO4 precipitate using Population balance modelling coupled with CFD, where we have two reactants (BaCl2 and Na2SO4) fed into the reactor which has two inlets forming the product BaSO4 crystals in the reactor after both the reactants mix. The reaction is as follows
BaCl2 (liq phase) + Na2SO4 (Liq phase)-----> BaSO4 (precipitate)
Here I defined both the reactants (BaCl2 and Na2SO4) as primary phases and BaSO4 as secondary phase.
Both the reactants were defined with water liquid properties except their mol.wt (BaCl2=208.23 and Na2SO4=142) from the literature. Then the BaSO4 was defined with density of solid crystals and its mol.wt.
Initially I obtained flow field without species transport model. Then I activated the multiphase Eulerian model the activated the Population balance model, here for now I am using the QMOM method.
In the inlet Boundary conditions for both reactants which are fed in separate inlets the mass fraction is defined. For secondary phase the inlets volume fraction is defined as zero as they are not the reactants. Then I define the outlet boundary conditions for secondary phase as one. In the Phase interaction Reactions panel I defined two rectatnts and 1 product and the reaction rate function as population balance variable.
Until now i have done these steps.
Is these steps right? because I am not able to solve or obtain any solution for secondary phase as the residuals show zero for the secondary phase and the moments are all zero. should I define any value for Moments? as I defined zero. And also I am getting divergence if I try to do these stepshere I am using the calculated values for nucleation and growth without using UDF, do you recommend UDF to define the nucleation and growth values.

Your help, feedback and guidance will be highly appreciated. thanks in advance

Sorry I know that my questions is very long

Hello,

the C_YI(cell,tp,0)

here zero is the species index.

You can check the sequence in the material panel for which it corresponds. normally it is in the same sequence. or you may write a UDF to identify it looping over all the species.


Thiru

Hy mohamad ashar what did you do for simulation, i simulate the crystalization in fluent i do this steps like you but the residual always is zero i don what I do.

Hi,

I am working on a similar problem, the difference is that I am modeling the calcium phosphate precipitation obtained from the reaction of calcium nitrate and diammonium phosphate and I have a similar problem. I would like to ask if you have succeeded to resolve this issue?

Thanks,
Botond

Luo aggregation kernel
 

Hi Chittipo,

I want to write a UDF for Luo aggregation kernel, same as the built-in one in Fluent. However, there are some problems.
Can you tell me how I can insert the "number density of bin i" into the UDF from the Fluent? Because in the DEFINE_PB_COALESCENCE_RATE macro there is no argument for number density. Is there any other way to find out the number density for bin i related to the d_1 (the argument for the macro)? even through RP_GET_REAL,...?

Thank you
Shaham

Hiii Chittipo,

I am using "Prince and Blanch(1990) coalescence model and Luo & Svendsen(1996) break up model in simulation.

I unable to write UDF terms for number density for bubble.Is there any terms to represent number density ??

Thank you,

Right now Im confused about the breakage process model:

Please see the image attached.

Hi Dear Chittipo, thanks a lot for your generosity, i'm now a student studying for my master's degree in china. Recently i have been reasearching on the process of 'submerged combustion', i.e. a water bath is heated by the gas generated by the burning of methane, in which case the gas is sprayed in in the form of bubbles. And i need to figure out the flow and heat transfer process, finally calculating the heat transfer coefficient by the temperatures we get by simulation.
first i wonder if the PBM is helpful in my case.
second i've been frustrated which method i should choose, discrete, smm or qmom? and since i don't konw actually the diameter range of the bubbles in my case, how should i input the relavant parameters?
i've been frustrated for a long time....:((((( i would apreciate it so much if you give me some tips and maybe some practising tuturial examples...
thanks so much

Hi!

How to load the population balance module in ansys fluent?
I was trying with /define/models/addon-module and then PBM.
But problem is that add-on module option is not coming in my fluent.

What to do with this?

Please someone answer.

Thanks
Vivekananda

Vivekananda,
Turn on the multiphase model in Fluent before doing that

Regards

Max diam
 

Do everyone know how we specify the maximum size of the particle?
I mean for choosing the max dia, we should notice what reason? or choosing Max dia is arbitrary

You should expect a max diameter in order to have your Particle Size Distribution fully defined in that range. In other words, you have to define a range that even if you make it bigger, the result will not be different. For example, I am actually using this following range : [2.4e-10m;8e-6m], for nucleation/growth/coagulation of carbon particles.